1. Field of the Invention
This invention relates generally to applications for using illuminated displays, and more particularly, for integrating electroluminescent light emitting panels with articles of fabric or textiles.
2. Problem
Electroluminescent (EL) panels or lamps provide illumination for a wide array of objects such as watches, vehicle instrument panels, computer monitors, etc. These EL panels are typically formed by positioning an electroluminescent material, such as phosphor, between two electrodes, one of which is essentially transparent. The electric field created by applying an electric current to the electrodes causes excitation of the electroluminescent material and emission of light therefrom, which is viewed through the transparent electrode. Advancements in materials science have led to the formation of EL panels from thin, elongate, flexible strips of laminated material having a variety of shapes and sizes.
It is desired to have an illuminated display integrated into a fabric or textile application, such that a light source can be created on clothing, backpacks, tents, signs, and the like. However, forming an electroluminescent panel onto fabric presents a particular challenge because of the flexible nature of fabric and the uses to which it is put, such as being worn as an article of clothing. Unlike an EL panel hung on a wall or in a window, electroluminescent panels attached to fabric must be put through repeated cycles of physical stress from flexion of the fabric, and must be properly electrically and thermally insulated due to the increased risk of being touched by a person or worn close to their body. Additionally, fabrics and textiles have generally proven to be difficult substrates upon which to build the component layers of an EL panel. What is needed is a process for better integrating an EL panel with a fabric section to form a unitary illuminated display system.
Electroluminescent film is commonly used in the display industry as back-lighting for liquid crystal displays. As constructed today, these films are not transparent, or even semi-transparent since the back electrode is either carbon or silver. It is thus also desirable to have a large area illumination source that is semi-transparent, i.e. it allows the observer to see an object through the back-side of the device while it is illuminating the object.
Solution
The present invention involves processes for reliably forming the component layers of an electroluminescent panel onto a fabric section to facilitate construction of the entire EL panel assembly. In one aspect, the layers of an electroluminescent panel are formed integral with a substrate section. First, a rear electrode made of a conductive polymer is formed onto a substrate section in a desired pattern. Then, a dielectric layer is formed over the rear electrode layer. A light emitting layer, transparent conductive layer made of a conductive polymer, and front electrode lead are then successively formed onto the substrate section; the light emitting layer atop the dielectric layer and the transparent conductive polymer layer atop the light emitting layer. Each of the component layers of the EL panel may be formed onto the substrate section by a printing process. Optionally, the substrate section can be adhered to a substantially rigid backing while the EL panel component layers are applied to aid in accurate placement of such layers. This aspect provides a construction where at least the rear electrode is more fully integrated with the substrate section. When an electric current is applied to the front and rear electrodes, an electric field is created to excite the light emitting layer to illuminate.
Another aspect of the present invention provides a process whereby the rear electrode of an EL panel is formed directly onto a fabric section using a metalization process. An image is first formed to define a specific design to be illuminated. The image is placed over a fabric section to define an area for display and a catalyst is applied to such display area. Next, the portion of the fabric section with catalyst applied thereto is immersed in an electroless plating bath and subsequently removed, which allows a chemical reduction to occur in the aqueous solution. Finally, the fabric section display area is immersed in an electrode bath to form an electrode layer that is integrated with the fabric section and patterned in the associated image. The rest of the layers of the EL panel, including a front electrode, may be formed on top of the rear electrode and base fabric section by, for example, a printing process. Upon energizing the EL panel, a light emitting layer will illuminate in the pattern of the image.
In still another aspect of the present invention, an insulative layer and a process for forming thereof is provided to encapsulate a fabric section having a rear electrode. The fabric section is first immersed in electrophoretic liquid. An electrical lead is connected to the rear electrode and a counter electrode is immersed in the liquid and connected to an electrical lead of opposite polarity. Upon a voltage being applied to the electrical leads, an insulative conformal coating is deposited on the fabric section immersed in the electrophoretic liquid. This coating maintains the integrity of the rear electrode and electrically insulates such electrode, thereby mitigating the risk of electrical shock for a person touching the fabric. Furthermore, the coating may serve as the dielectric layer of the electroluminescent panel. A printing process or other means may be used to form the remaining layers of an EL panel on top of the dielectric layer.
By these processes, safer, more durable illuminated display systems can be manufactured for all types of fabric and textile applications, such as safety clothing (vests, jackets, hats, gloves), outdoor gear (tents, backpacks, etc.), flags and signs, or any other application requiring a flexible illumination solution. Additionally, because the EL panel components of the illuminated display system may be formed together as thin layers by, for example, a printing process, thin EL lamps may be formed that are not too bulky or cumbersome to be worn on an article of clothing. As opposed to reflective strips, the illuminated displays systems formed by these processes do not require light to be reflected off of an EL panel surface from external light sources. Other advantages and components of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings, which constitute a part of this specification and wherein are set forth exemplary embodiments of the present invention to illustrate various features thereof.